1. Field of the Invention
The present invention relates first of all to an automatic surveillance process for a site in which the occurrence of incidental events is awaited, and according to which a recording is made, on an erasable medium of finite storage capacity, of data collected at the time of occurrence of an awaited event.
Here, the term "site" used in the present context should be understood in its broadest definition. Among other things, it can encompass a communications link (such as a road junction), a commercial site (e.g. a warehouse), an industrial site (e.g. nuclear power station), or a private site (e.g. a dwelling). The common denominator to all the sites to which the inventive process is applicable is that they can be the scene of provoked or unprovoked events all having a random nature, i.e. which are probable but unpredictable, with more or less serious consequences. In general, it is not possible to analyze the cause or conditions of occurrence of such events or even to acquire a proof that such an event has really taken place, in the absence of automatic recording.
2. Description of the Prior Art
Various procedures are known to ensure the surveillance of specific sites--highways, commercial and industrial premises--based on networks of cameras whose images are analyzed in real time by security personnel. Because of the large cost of maintaining personnel 24 hours a day, these procedures are confined to very high risk security situations where it is necessary to intercept assault and robbery attempts.
In the absence of round-the-clock personnel, events with a very low repetition rate require such long recordings for their surveillance, that it would be necessary to resort to multiple reloadings of the recording medium, and these opertions can be subject to neglect, delays, and are besides considerably cost intensive. Consequently, it is easy to imagine the probability of an awaited event not being recorded. Moreover, the subsequent exploitation of such continuous recordings call for the very lengthy process of playing back and viewing the complete recording to seek the relatively short useful part on which the event is recorded.